Plastic bags are used for many purposes, including transporting and storing pourable substances. In many applications, reclosable bags are preferred because they can be closed to seal pourable substances or other contents within, and subsequently repeatedly opened and closed as desired. Typically, the plastic bags are made reclosable by means of a matingly engageable zipper-like releasably locking closure.
The general principles for making plastic bags are fairly well-known and are typified in numerous prior patents. A method of manufacturing the plastic bags includes extruding molten material through an annular opening of a die assembly to produce a tubular film that is later flattened, sealed, and cut into individual bags. The annular opening of the die assembly typically includes profile openings to provide male and female profiles that are integral to the tubular film. However, the profile openings make the annular opening asymmetrical. Material moves more easily through the regions of the annular opening near the profile openings to the detriment of the regions of the annular opening that are distanced from the profile openings. The impact is greatest at the region of the annular opening through which the tubular film that forms the bottom end of the bag is extruded. Accordingly, the bottom end of the bag can have a thickness that is unintentionally thinned and that can easily break or crack, particularly under extreme temperature conditions. Simply thickening the unintentionally thinned portion by widening the annular opening in the affected region is a potential, although flawed, solution to this problem since increasing the thickness of the tubular film in the affected region can make the tubular film difficult to flatten, fold, or otherwise handle during the process of forming individual bags. In general, it is desirable to control the characteristics of the tubular film, such as thickness, rigidity, and flexibility, without wasting material or negatively impacting the performance of the tubular film.
Another problem with existing plastic bags is that it is difficult to pour a liquid or other pourable substance from the bags. For example, the user may bend a lip of a plastic bag into a V-shaped channel through which the pourable substance can be directed. However, the flimsiness of the film and the length of the cantilevered lip results in the channel collapsing or flexing under the weight of the pourable substance. Thus, the channel formed by the lip is not suitable to control the direction of flow of the pourable substance from the bag.
Therefore, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies. What is needed is a plastic bag that is less susceptible to cracking and breaking and that has an improved pour feature.